Nanocomposites, including nanoparticles of semiconductor metal oxide (MO) and reduced graphene oxide (rGO), are of exceptional interest for light-activated gas sensors functioning without thermal heating. In this paper, we discuss the sensor properties of electrospun ZnO nanofibers and ZnO/rGO composites. The materials were characterized by transmission and scanning electron microscopy (TEM, SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and IR spectroscopy (FTIR). The sensor characteristics were studied when detecting reducing gases CO, H₂, and NH₃ and oxidizing gases NO and NO₂ at 25–150 °C in dark conditions and under UV illumination. ZnO nanofibers and ZnO/rGO composites have no sensitivity when detecting CO, NH₃, and H₂ either in dark conditions or under UV illumination. At T = 25 °C, UV illumination is a necessary condition for the appearance of a sensor response when detecting both NO and NO₂. The increased sensitivity of ZnO/rGO composites when detecting nitrogen oxides at T = 25 °C is discussed in terms of the heterojunction formation. Observed at T = 150 °C, opposite trends in the UV illumination influence on the sensor response toward NO and NO₂ are due to the participation of chemisorbed oxygen in the processes responsible for the sensor response formation when detecting NO.

In this work, we report the synthesis of perovskite-type Ba-doped LaFeO₃ (La_1−xBa_xFeO₃, x = 0.00, 0.02, 0.04, and 0.06) nanofibers (NFs) using the electrospinning method. The synthesized La_1−xBa_xFeO₃ materials have a fibrous structure with an average fiber diameter of 250 nm. The fibers, in turn, consist of smaller crystalline particles of 20–50 nm in size. The sensor properties of La_1−xBa_xFeO₃ nanofibers were studied when detecting 20 ppm CO, CH₄, methanol, and acetone in dry air in the temperature range of 50–350 °C. Doping with barium leads to a significant increase in sensor response and a decrease in operating temperature when detecting volatile organic compounds (VOCs). The process of acetone oxidation on the surface of the most sensitive La_0.98Ba_0.02FeO₃ material was studied using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and temperature-programmed desorption in combination with mass spectrometry (TPD-MS). A mechanism for the sensor signal formation is proposed.